U.S. patent number 4,438,752 [Application Number 06/299,490] was granted by the patent office on 1984-03-27 for vehicle ignition system.
Invention is credited to William S. H. Cheung.
United States Patent |
4,438,752 |
Cheung |
March 27, 1984 |
Vehicle ignition system
Abstract
A vehicle ignition system comprises a transformer having a
primary winding and a secondary winding for providing the desired
high voltage to the spark plug of the vehicle engine and a circuit
including a further winding for said transformer connected across a
switch and a load. The switch is operable only by a security device
and when it is closed, the load absorbs energy from the transformer
so that insufficient voltage is generated at the spark plug and the
vehicle is immobilized. The load can be replaced by a reverse flux
generator, the reverse flux opposing that generated by the primary
winding. The security device may comprise a conventional key and
keyhole, or more sophisticated devices such as code readers which
read a code inputted from a magnetic card or from a keyboard.
Further security may be provided by a further switch in series with
the primary winding and battery, the further switch being operable
in synchronism with and in the opposite sense to the first
mentioned switch.
Inventors: |
Cheung; William S. H. (Hong
Kong, HK) |
Family
ID: |
10523492 |
Appl.
No.: |
06/299,490 |
Filed: |
September 4, 1981 |
Foreign Application Priority Data
|
|
|
|
|
Jul 24, 1981 [GB] |
|
|
8122957 |
|
Current U.S.
Class: |
123/630;
123/146.5B; 123/198B; 123/198D; 180/287 |
Current CPC
Class: |
B60R
25/045 (20130101) |
Current International
Class: |
B60R
25/04 (20060101); B60R 025/00 () |
Field of
Search: |
;123/630,198B,146.5B,198D ;180/287 ;307/1AT ;340/63,64 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
54-47912 |
|
Dec 1979 |
|
JP |
|
671742 |
|
May 1952 |
|
GB |
|
1258120 |
|
Dec 1971 |
|
GB |
|
Primary Examiner: Lall; Parshotam S.
Attorney, Agent or Firm: Pollock, Vande Sande &
Priddy
Claims
What is claimed is:
1. A vehicle ignition system comprising:
a transformer having a primary winding, secondary winding and
auxiliary winding;
means for alternately connecting said primary winding to a voltage
source whereby a magnetic flux is generated, said magnetic flux
inducing an ignition current in said secondary winding;
a security switch means serially connecting a power dissipating
load to said auxiliary winding, said load reducing said secondary
winding current prohibiting an ignition current of sufficient
magnitude for providing ignition to said vehicle;
a comparator for opening said security switch meansin response to a
unique input code; and
means for supplying a unique code to said comparator whereby said
vehicle ignition current is restored upon detection of said unique
code.
2. A system as claimed in claim 1 wherein said means for supplying
comprises a magnetic card reader, the switch means being openable
only when a magnetic card with a predetermined code is inserted
into the card reader.
3. A system as claimed in claim 1, wherein the coil has a primary
winding and the system comprises a further switch in series with
said primary winding, the further switch being normally open, but
connected for closing in synchronism with the opening of said
normally closed switch.
4. A system as claimed in claim 1, wherein the means for supplying
comprises a keyboard.
5. A vehicle ignition circuit comprising:
a transformer having a primary winding serially connected at a
first junction with an auxiliary winding, and, secondary
winding;
a switching means connecting said auxiliary winding free end with
said primary winding free end forming a second junction;
means for applying a voltage potential between the first junction
of said primary and auxiliary winding and the junction of said
switch means and said primary winding whereby a current flows
through said primary winding;
magnetic card reading means connected to enable and disable said
switching means, whereby said switching means when enabled,
provides for a current through said auxiliary winding, cancelling a
flux generated by said primary windings, and when said switching
means is disabled, inhibiting current flow through said auxiliary
winding whereby said secondary winding produces an ignition current
in response to said primary winding current.
6. The ignition system of claim 5 further including a second
switching means operable from a keylock and connected to interrupt
a current flow in said primary and auxiliary winding when said
magnetic card reading means is enabling said first switching means,
whereby operation of said vehicle requires both closing said second
switching means and opening said first switching means.
7. The vehicle ignition system of claim 5, wherein said means
connected to said auxiliary winding includes a current path for
dissipating a current induced in said auxiliary winding.
8. The vehicle ignition system of claim 5, further comprising means
for indicating when a current is supplied to said auxiliary
winding.
Description
BACKGROUND OF THE INVENTION
Conventional vehicle ignition systems include a switch operated by
a key to connect the vehicle battery to the ignition coil. This
arrangement is not very secure, and thieves have been able to
energize the vehicle engine by short-circuiting the switch operated
by the key.
Additional vehicle security systems have been proposed, independent
of the ignition system, for example causing an alarm to sound if
the vehicle is tampered with, but if the alarm is itself disabled,
it is still possible to dive away the vehicle by short-circuiting
the ignition switch.
SUMMARY OF THE INVENTION
The present invention has the object of providing an additional
security device within the ignition system which disables the
system for illicit use independent of the possible short-circuiting
of the ignition switch.
According to this invention there is provided a vehicle ignition
system comprising a transformer having a primary winding and a
secondary winding for providing the desired high voltage to the
engine and a circuit including a further winding of said
transformer which circuit when activated prevents sufficient
magnetic flux in the system from reaching said secondary winding to
provide the desired high voltage to the engine, the circuitbeing
activated by a switch is normally closed and which is openable only
by a security device. The security device may comprise a
conventional key, but more sophisticated security devices include a
coded magnetic card and card-reader, or a comparator which compares
a code fed into the device with a preset code.
A further switch may be provided in the system in series with the
primary winding of the transformer, the further switch being
normally open, but closed in synchronism with the opening of the
first switch under the control of the security device.
DESCRIPTION OF THE FIGURES
FIG. 1 is a schematic drawing of a first embodiment of the
invention for providing a secure ignition system.
FIG. 2 is a schematic drawing of an embodiment of the invention
using conventional components.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Examples of the invention will now be described with reference to
the drawing FIG. 1 which is a circuit diagram of an ignition system
for a vehicle.
In the figure, the ignition coil generally indicated at 11 has a
primary winding 12, a conventional secondary winding 13 and an
additional auxiliary winding 14. One terminal of the primary
winding 12 is connected through a pair of contacts 15 of the
distributor to the earthed terminal of the battery 16. The other
terminal of the primary winding 12 is connected through a switch 17
to be described to the other terminal of the battery 16. A
conventional ignition switch is not shown in the drawing, but if
provided, would be located in series with the switch 17.
The first terminal of the primary winding and one terminal of the
conventional secondary winding 13 of the coil 11 are connected
together through a capacitor 18 to earth. The other terminal of the
winding 13 provides the high voltage required for the vehicle
engine, and in the drawing is shown being connected to a spark plug
19 in the engine.
The additional auxiliary winding 14 is connected across a device 21
and switch 22. The switches 17 and 22 are operable in response to
electrical signals, and can comprise a triac, SCR, or any suitable
semiconductor switch. The electrical signal to actuate the switches
is provided by a comparator 23, which is fed with a signal from a
preset data coding device 24 and compares this with the output of a
code reader 25 into which the intending user of the vehicle inserts
a code. If the inserted code is correct, the comparator 23 produces
an electrical signal which is fed through an inverter 26 to cause
the switch 22 to open and through a further inverter 27 to cause
the switch 17 to close. When the comparator 23 produces the
electrical signal, the battery 16 energizes the primary winding of
the coil, and the additional auxiliary winding 14 produces no
effect on the coil 11 since the switch 22 is open. The power from
the winding 12 is therefore transferred to the secondary winding 13
and the spark plug 19. However, when the correct code is not fed
into the reader 25, the comparator 23 does not produce an
electrical signal and the switch 22 remains closed and the switch
17 remains open.
The device 21 can be a load, whose connection across the coil 14 by
the switch 22 absorbs at least a substantial amount of the power
from the winding 12 so that there is insufficient energy, if any,
to energize the spark plug 19 through the coil 13.
Alternatively the device 21 can be a reverse flux generator, which
passes a current through the coil to generate a flux in the
transformer core which is approximately equal and opposite to that
generated by the primary winding 12. The resultant flux at the
winding 13 is therefore little or nothing, so that the spark plug
19 is not energized.
The opening of the switch 17 disconnects the battery 16 from the
primary winding 12. Even if an illicit user manages to
short-circuit the switch 17 in the same way as the conventional
thief short-circuits the conventional ignition switch, the device
21 connected across the secondary winding 14 will prevent
sufficient energy reaching the spark plug 19. The additional
winding 14, the device 21 and the switch 22 can be encapsulated
within the coil so that it is not possible or at least very
difficult for the illicit user to cancel the effect of the winding
14.
The provision of the switch 17 makes the conventional ignition
switch unnecessary. A key may be used to input the code into the
code reader 25, but if desired a magnetic card may be used or even
a keyboard may be provided for the user to feed the code into the
code reader.
Referring now to FIG. 2, another embodiment of the invention is
shown. In this embodiment, the circuitry 29 for actuating switches
22 and 17 is replaced by a single integrated circuit 31,
manufactured by LS1 Computer System Inc., known to those skilled in
the art as part no. LS7225. Connected to the input ports 10-14 is a
code generator which may be the same as code reader 25 of FIG. 1.
Any device such as a magnetic card or thumbwheel binary digit
generator may serve as code generator 25. Integrated circuit 31
will provide first and second enabling voltages on ports 7 and 8
when the proper code is applied to ports 10-14. Indicator 32, which
may be a light emitting diode indicates the condition of the
ignition system as either locked or unlocked.
Silicon controlled rectifier 33 takes the place of switch 17 of
FIG. 1. When the gate of SCR 33 is enabled, equal and opposite
currents flow through windings 12 and 14. The flux produced from
primary winding 12 is cancelled by the flux produced by auxiliary
winding 14. Thus, secondary winding 13 receives only a residual
flux insufficient to produce a spark producing voltage. Also relay
winding 35a is deenergized in the locked condition opening contacts
35b.
When the proper code has been reviewed by integrated circuit 31, no
enabling voltage occurs at port 7 and therefore SCR 33 is rendered
non-conducting. Also, port 8 applies a voltage for energizing relay
winding 35a. Contacts 35b therefore assumes a closed condition
permitting primary winding 12 to generate a flux for inducing a
spark generating voltage in secondary winding 13.
Although the conventional firing system for an internal combustion
engine has been shown with mechanical contacts 15, the invention
can clearly be applied to other ignition systems, including
electronic systems.
* * * * *